1. Field of the Invention
The present invention relates to optically active 4-substituted-2-hydroxybutanoates which are useful as starting materials for medical agents and to a process for producing them.
2. Descriptions of the Prior Art
Optically active 4-substituted-2-hydroxybutanoates of the present invention are useful as starting materials of many medical agents. However, there has been no effective process so that racemic methyl 4-chloro-2-hydroxybutanoate, racemic methyl 4-bromo-2-hydroxybutanoate and the like were used (European Patent Laid-open Application No. 233728, etc.).
Recently, when racemic compounds are used as medical agents, it is necessary to examine the physiological activity of two enantiomorphs, because the physiologically activities may be different. Further, when a compound having a stereostructure has especially strong physiological activity, it is earnestly required to construct only a compound having the desired stereostructure, considering the efficiency and safety.